The invention relates to an at least partially rotational and percussively driven rock drill for cutting away rock-substance such as concrete and masonry.
Rock drills of this type comprise an extended, helical shaft that has, at one end, an insertion end for receiving a driving tool device and, at the opposite end, a tool head with cutting edges made of hard material. In a rock drill with auxiliary cutting edges there are frequently radially smaller auxiliary helices arranged between the main helices associated with the main cutting edges.
The tool head and the helices wear radially due to the direct wear from contact with the sides of the bore hole when cutting hard stone. The radial wear is a measure of the service life of the rock drill.
DE1965131A1 discloses a rock drill that has circumferential ridges or axis-parallel grooves of a particular depth on the helical spines that serve as wear indicators for wear resulting from direct contact with the sides of the bore hole. DE19859624 discloses a rock drill, wherein wear indicators are filled with color, in the spine of the helix, to visibly display sufficient remaining depth of the wear indicator. The low tolerable radial wear makes determination of wear difficult.
U.S. Pat. No. 4,904,130 discloses a rock drill, wherein a color coating in the floor of the groove acts as an indicator marking for drilling depth, which is subject to groove wear by the material cuttings.